Re: Performance 8.4.0

* Robert Haas (robertmhaas(at)gmail(dot)com) wrote:
> On Fri, Jul 31, 2009 at 12:22 AM, Chris Dunn<chris(dot)dunn(at)bigredsky(dot)com> wrote:
> > constraint_exclusion = on
>
> This is critical if you need it, but a waste of CPU time if you don't.
> Other than that your paramaters look good. Are you using the default
> page cost settings? I see you have 12 GB RAM; how big is your
> database?

With 8.4, you can set 'constraint_exclusion = partition', where it'll
handle inheirited tables and UNION ALL queries but not other possible
cases. It's set that way by default, and is pretty inexpensive to leave
in place (since it only gets tried when it's likely you want it).

I'd recommend setting it to partition under 8.4 rather than disabling it
entirely. Under older versions, set it to 'off' if you don't need it.

Thanks,

Stephen